A vehicle door lock control apparatus for a keyless entry system is disclosed in, for example, Japanese Patent Laid-Open Publication Nos. 60-65875, 60-65876 and 60-65877. Further, the Cedric/Grolia's new-model explanation manual, issued in June 1991 by Nissan Motor Co., Ltd., discloses a card entry system. The card entry system has a request switch which is mounted on the vehicle body, a card (remote controller) and a controller. If the user operates the request switch, a request ID (identification) code is transmitted to the card. The request ID code is collated with the memorized code in the card. If the request ID code corresponds to a memorized code, the card transmits an entry ID code to the controller. If the entry ID code corresponds to the memorized code in the controller, the controller instructs the door lock controller so that the vehicle door is placed in the unlocked condition.
This type of system adopts an electromagnetic induction affect to establish communication between the card and the controller. In this system, an extra antenna is necessary to establish communication between the card and the controller. Because the card does not have a manual operating function, it is not possible to instruct the controller from the card. Further, the card is so small that the user is apt to inadvertently leave the card behind.